Mineralocorticoid-like steroids other than aldosterone have been postulated to be elevated in low-renin "essential" hypertension and therefore to contribute to the elevated blood pressure in the disease. In the proposed studies we plan to develop a radioreceptor assay for quantifying plasma mineralocorticoid activity due to steroids which act through the renal aldosterone receptor by measuring the ability of plasmas to inhibit the binding of radioactive aldosterone by these receptors. BIBLIOGRAPHIC REFERENCES: Ballard, P. L., Carter, J.P., Graham, B. S. and Baxter, J. D., A. radioreceptor assay for evaluation of the plasma glucocorticoid activity of natural and synthetic steroids in man. J. Clin. Endocr. 41, 290-304 (1975). Baxter, J. D., Schambelan, M., Matulich, D. T., Spindler, B. J., Taylor, A. A. and Bartter, F.C., Aldosterone receptors in human and rat kidney, and the evaluation of plasma mineralocorticoid activity in normal and hypertensive states (abst.) Proceedings of the Fourth Meeting of the International Society of Hypertension, Sydney, Australia, Feb., 1976.